Model 750 User Manual

1 Introduction

The Model 750 is a mini pulse and delay generator providing up to 8 independent delayed pulses at up to 50 MHz. The base unit ships with 4 channels; an 8-channel version is available with the channel-extension option.

Delays up to 100 seconds can be programmed with 100 ps resolution and channel-to-channel jitter under 50 ps RMS. An option enhances delay resolution to 1 ps. SMB outputs deliver 1.5 V to 5 V, 1 ns rise-time pulses into 50 Ω, with amplitude, polarity, burst count, and width independently adjustable per channel.

Two trigger inputs and three internal synchronized timers (0.01 Hz to 50 MHz), plus a software command, can trigger all selected delay channels, each set to single-shot or repetitive. With its multi-trigger system, the Model 750 can be thought of as up to four independent generators in a single box.

The unit uses an internal 100 MHz TCXO clock reference, or an external user-programmable clock from 10 MHz to 240 MHz. Parameters are controlled remotely from a standard PC browser, or via USB-to-UART and Ethernet. A multi-channel Real-Time Chart View lets you visualize every channel output on a common time chart, with zoom for fine timing detail.

Package Contents

The box you receive should contain the following:

• Model 750 pulse & delay generator
• AC/DC compact power supply and power cord
• USB and Ethernet cables
• USB drive with the PDF user manual and USB control software
• Certificate of calibration

Notify Berkeley Nucleonics if the unit appears damaged in any way. The Model 750 ships in an antistatic package to guard against electrostatic damage — inspect the unit for loose components before use.

Power Source and Operating Temperature

The supplied power supply operates from 80 V to 264 V AC (47–63 Hz) and delivers +5 V DC at up to 4 A. It is internally earthed to avoid hazardous potential on the case; do not substitute a power supply from another product, and do not apply voltage to the shield or outputs.

The Model 750 operates at an ambient temperature of 10°C to 35°C (50–95°F), and can be stored from −10°C to +60°C (15–140°F). It is cooled by air circulation.

Power On & Self-Test

After connecting power, all front-panel LEDs should be off. A brief press of the front-panel ON/OFF button (which doubles as RUN/STOP) lights the TRIG, channel, and Lock LEDs briefly; the TRIG and channel LEDs then blink for a few seconds before turning off, and the ON/OFF button lights yellow (STOP state). The unit is ready once the Lock LED glows green, indicating the internal system clock is locked.

To power off, press and hold the ON/OFF button for more than 5 seconds; all LEDs turn off. An Auto-Power-On mode is available for embedded/OEM applications on request — contact Berkeley Nucleonics to enable it.

Getting Help

This guide is the main reference for operating the Model 750. If you need further assistance, contact Berkeley Nucleonics technical support at 800-234-7858 or info@berkeleynucleonics.com, and have your unit’s serial number ready.

2 Operating Principles

A time-base function provides a 200 MHz time base from an internal reference or from an external 10–240 MHz reference; the internal time base is also available on the rear-panel clock output. The trigger controller supports two modes:

• External trigger mode: a rising edge on the front-panel TRIG input triggers all delay channels. Each channel's rate can be single-shot, repetitive, or inhibited. A prescaler divides the trigger input frequency by an integer from 1 to 1,000,000,000.
• Internal trigger mode: delay channels are triggered from three frequency-programmable timers. Each channel's rate can be single-shot, repetitive, burst, or inhibited.

The Gate input quickly inhibits all or selected channel outputs, and can be reconfigured as a second external trigger. The RUN/STOP button enables or disables the output for all delay channels.

Delay Channels & Output

There are 4 independent delay channels (8 with the channel-extension option). Delay from the selected trigger source is programmable up to 100 seconds, in 100 ps increments (1 ps with the resolution option). Each output pulse (T1–T4, and T5–T8 with the extension option) is independently adjustable in level (1.5 V to 5 V in 10 mV steps), width (10 ns to 10 s in 5 ns steps), and polarity, and may be ORed with other outputs in its group of four. Outputs are designed to drive a 50 Ω load; on a high-impedance load, output level doubles (3.0 V to 10 V). A narrow-pulse mode, available with the resolution option, couples two delay channels — one starting the pulse, one stopping it — for pulse widths as narrow as 3 ns, precisely and independently adjustable in 1 ps steps.

Example Channel-Output Modes

The Model 750's trigger sources combine to produce several common patterns:

• Repetitive and single: different channels independently repetitive from different timers, or single-shot from a software command.
• Burst and MUX: a channel repeats a burst of N pulses per trigger; a MUX channel ORs two or more channels onto one output.
• Prescaler and gate: a channel divides down a fast external trigger with its prescaler, while a gate signal inhibits selected channels during part of the cycle.
• Pulse picking: a single output pulse is picked out of a fast external clock or trigger train, synchronized to one of the internal timers.

Delay Jitter & Accuracy

Jitter is the delay uncertainty of a channel output edge between successive triggers, measured in RMS picoseconds over an observation period of up to 10 seconds: under 50 ps + delay × 10^-7 channel-to-channel, and under 1 ns from an external trigger to any channel. Delay accuracy is the difference between the programmed and measured delay value, referenced against a channel programmed with delay = 0, averaged over 1000 measurements at a 1 kHz rate: under 500 ps + delay × 10^-6.

Maximum allowed power consumption, internal temperature, and minimum supply voltage are continuously monitored by the embedded software and reported in the control panel's status area. If any value reaches its limit, the overload indicator lights and the unit automatically stops; reduce the trigger rate below 1 MHz to clear the condition, then click the control panel's overload indicator to acknowledge it.

Front & Rear Panel

The front panel carries a TRIG input, one SMB output per channel, and status LEDs: TRIG (blinks on external trigger), per-channel output LEDs (blink at channel recurrence), RUN/STOP (also the power switch — yellow when stopped, green when running), Comm (USB traffic), Ext Clk (running on external clock), and Lock (internal clock system locked, lights green once the unit is ready). A short press of RUN/STOP starts or stops the trigger system; holding it for about 5 seconds powers the unit off.

The rear panel carries a Gate/Trig SMB connector, Clock In and Clock Out SMB connectors, a USB micro-AB connector, an RJ45 Ethernet connector, a GPIO connector (SMH-103 Samtec), and a +5 V DC power jack, along with Gate (blinks when the Gate input is active), Over Current, USB Link, and Ext DC indicator LEDs. A grounding screw is also provided. Powering the unit from USB alone may limit the maximum current draw to 500 mA, which can restrict output performance and available configuration.

GPIO Interface

Four GPIO lines on the rear panel are individually configurable as input or output under software command. Input levels run 1–2.3 V, input impedance is >20 kΩ; output levels run 0.1–3 V with 100 Ω output impedance and 5 ns rise/fall time. An optional cable breaks the GPIO connector out to a standard DB9.

3 Remote Control & Software

The Model 750 can be controlled two ways: an Easy remote path over Ethernet through the unit's embedded web server (no software install required), and a General remote path over Ethernet or USB using the included control software or your own application.

Easy Remote: the Web Control Panel

After connecting the Model 750's Ethernet port to your network and powering it on, enter the unit's IP address into any standard browser (Chrome, Firefox, or Edge) to open the control panel automatically. The default IP address is 192.168.0.10, netmask 255.0.0.0, gateway 192.168.0.1; if the address is ever lost, hold the internal reset button (accessible through the rear-panel "RAZ" hole) during power-up to restore it, or query it over USB with NETWORK:IPADDRESS?.

The main menu displays and controls the trigger and clock system (level, prescaler, external clock, clock output, three internal generators), the delay channel table (trigger source, rate, delay, amplitude, width, polarity), a RUN button, and a Trigger button for single-shot channels. An Extended Setup panel exposes per-channel burst count/period, gate enable, and MUX grouping. A Parameters page lets you change the IP address and other network settings, and a GPIO page configures the four I/O lines. All settings are stored and saved on the unit itself, so the control panel simply reflects the instrument's current state.

The following factory-default values apply out of the box, or after a reset:

Setting Up a First Pulse

As a worked example, here is how to produce a repetitive 1 Hz, 5 V, 1 µs pulse on channel T1 from the web control panel:

1. Connect the Model 750's Ethernet port to your network and power it on; set your PC's IP address to 192.168.0.100 with netmask 255.0.0.0, then browse to 192.168.0.10:8080.
2. Set internal generator F1 to 1.000 Hz.
3. Set channel T1: trigger source F1, rate repetitive, delay 0 ps, width 1000 ns, amplitude 5000 mV, positive polarity.
4. Click RUN. The T1 indicator on the front panel blinks at 1 Hz; confirm the pulse on an oscilloscope, then click STOP to end it.

General Remote: USB and Ethernet

Over USB, the Model 750 presents a virtual serial (COM) port: 9600 baud, 8 data bits, 1 stop bit, no parity, no flow control. Any terminal emulator (PuTTY, for example) or the included control application can issue commands directly. Over Ethernet, the same ASCII command set is available on TCP port 4000; set the unit's IP address, netmask, and gateway either from the web control panel's Parameters page or with the NETWORK:* commands described in the Programming Reference below.

Free control software is provided for Windows and Linux, presenting the same interface as the web control panel. Both connect over USB and auto-detect the assigned COM port; if the Model 750 is plugged in over USB but not powered on with the front-panel button, the software will see the port but report a connection error until the unit is switched on.

4 Programming Reference

Every command below is sent as plain ASCII text terminated with <cr><lf>, over either the USB virtual COM port or an Ethernet connection to TCP port 4000. A command with a trailing ? is a query and returns the current value; most settings support both a SET form (with a parameter) and a ? query form. Multi-word commands use a colon between keywords, and a caret (^) in the syntax column below marks a single blank space.

Identification

Auto RUN

Two functions can be set to activate automatically at power-up. Auto RUN starts output pulses automatically once the unit powers on. Auto POWER makes the generator power on by itself at startup for embedded/OEM applications, and inhibits the RUN/STOP button while active — contact Berkeley Nucleonics to enable it.

Clock System

Gate & Trigger

Channel Configuration

GPIO

Status

Network

Programming Examples

Example 1 — repetitive pulse on T1 (width 10 µs, amplitude 4.5 V, rate 1 Hz):

On the front panel, the T1 indicator should blink at 1 Hz. Send RUN^OFF to stop.

Example 2 — a 2-pulse burst on T1 (width 10 µs, amplitude 4.5 V, rate 10 kHz):

Example 3 — combine T1 and T2 onto one output (T1: width 10 µs; T2: width 20 µs, delayed 20 µs; both at 4.5 V, 10 kHz):

C programming examples over the USB or Ethernet port are available on request from Berkeley Nucleonics.

5 Options

6 Glossary

Burst mode

A channel emits a fixed number of pulses (burst count) at a fixed period per trigger, instead of a single pulse.

Delay resolution

The smallest step by which a channel's delay can be adjusted — 100 ps standard, 1 ps with the resolution option.

Gate

An input that inhibits selected channel outputs while active; can alternately serve as a second trigger.

GPIO

General-purpose input/output lines, individually configurable and controlled over the remote command interface, independent of the delay-channel logic.

Jitter (RMS)

The statistical uncertainty in a channel's output edge timing between successive triggers, expressed as a root-mean-square value in picoseconds.

MUX mode

Logically ORing two or more channel outputs within a group of four onto a single output.

Narrow-pulse mode

A mode, available with the resolution option, that couples two delay channels — one starting, one stopping the pulse — to produce output pulses as narrow as 3 ns.

Prescaler

An integer divider applied to an external trigger input before it reaches the trigger controller, for triggering from a higher-rate source.

User set

One of 8 complete, named configurations of channel and clock settings that can be saved to and recalled from the unit's non-volatile memory.